B3: Organisation and Digestion Flashcards
What are tissues?
They are a group of cells with a similar structure and function working together. E.g. muscular tissue in stomach to churn food and digestive juices together.
What does the digestive system do?
The digestive system breaks down larger molecules into smaller ones so that they can be absorbed and used by cells.
What is the role of each part of the digestive system?
Glands (salivary glands/pancreas): Produce digestive juices containing enzymes to break down food.
Stomach: Produces hydrochloric acid to kill bacteria and provide optimum pH for protease enzyme to work.
Liver: Produces bile store in gall bladder, which helps with the digestion of lipids.
Large Intestine: Absorbs water from undigested foods to produce faeces.
Small Intestine: Soluble molecules are absorbed into the blood.
What are carbohydrates?
They provide us with the fuel/energy that we need (Sugar, starch, fibre).
They are made up of chains of simple sugars like glucose.
What is protein?
Protein is used for the growth and repair of body tissues.
It is made up of amino acids and can act as antibodies, enzymes or hormones.
What are lipids?
Lipids give us energy and provide insulation.
Made up of fatty acids and glycerol.
What is the test for starch?
Add orange/yellow iodine solution to the food sample using a pipette. If starch is present, it will turn to blue/black.
What is the test for sugar?
Add blue Benedict’s solution to food sample in a test tube. Place in hot water bath for a few minutes and heat gently. If there is sugar, colour will change to orange/red.
What is the test for protein?
Add a few drops of blue Buret’s reagent to food sample in a test tube. Shake the solution and if the result is positive then it will change to purple.
What is the test for lipids?
Add ethanol to a food sample and if lipids are present then a white precipitate will form.
What are the hazards of food tests?
Iodine solution is an irritant to the eyes so wear goggles. Biuret solution is corrosive so should wash hands if it gets on skin. Benedict’s is irritant. Ethanol is flammable.
What are the types of tissues in humans?
Muscular - contracts to move whatever it is attached to.
Glandular - makes and secretes chemicals like hormones and enzymes.
Epithelial - covers some parts of the body.
How do you prepare a food sample?
Use piece of food and break it up using a pestle and mortar. Add food to a beaker and add distilled water and stir the mixture, getting rid of any solid bits of food.
What are enzymes and what do they do?
They are proteins that act as biological catalysts to speed up the rate of chemical reactions in the body without being used up. They help to break up large molecules into smaller ones.
What is the lock and key theory?
It describes how the shape of the substrate is complementary to the uniquely shaped active site and bond to form an enzyme-substrate complex. The reaction takes place and the products are released.
How does temperature and pH affect the rate of reaction for enzymes?
The rate of reaction increases with an increase in temperature up to the optimum temperature. After this the active site of the enzyme will become denatured and the substrate will no longer be able to fit into it.
This is the same for pH, with different enzymes having different optimum pH meaning if it is too high or low the active site can become denatured - e.g. pepsin for proteins is 2 however most are neutral.
What do the different enzymes produce and where can they be produced?
• Carbohydrases (e.g. amylase) convert carbohydrates into simple sugar. They are produced in salivary glands, pancreas and small intestine.
• Proteases convert proteins into amino acids. They are produced in the stomach, pancreas and small intestine.
• Lipases convert lipids into fatty acids and glycerol. They are produced in the pancreas and small intestine.
What is bile and what does it do?
• Bile is produced in the liver and stored in the gall bladder and released into the small intestine.
- They are alkaline to neutralise the HCl in the stomach so that enzymes with a higher optimum pH can work there.
- They emulsify fats from larger droplets into smaller ones so that there is a larger surface area for enzymes to work on.
What is metabolism?
• It is the sum of all chemical reactions in the body or in a cell and are controlled by enzymes.
E.g. building large molecules from smaller ones - making glucose/amino acids.
Changing one molecule into another - glucose to fructose.
Breaking down large molecules into smaller ones - digestion, respiration.
Describe the experiment to investigate the effect of pH on enzyme activity.
- On each well of a spotting tile, label each one and add a drop of iodine solution to each one.
- Using a syringe, add 2cm^3 of each buffer solutions of different pH into each labelled test tube.
- Immerse starch solution, amylase solutions and test tubes of buffer solutions into a 25°C water bath and allow a few minutes for the temperature to equilibrate.
- Use syringe to add 2cm of amylase and starch solution into a tube of buffer solution.
- Start timing and use glass rod or pipette to transfer a drop of mixture into the first well.
- Add a drop every 30 seconds and record the time taken for solution to change back into an orange colour, to indicate that no starch is present.
- Calculate the rate of enzyme reaction using 1/time taken.
- Repeat using different pH values and plot rate of reaction in y axis against pH values in the x axis.
Make sure to control volume/concentration of the enzyme/starch solution.
